1.0 Field of the Disclosure
This disclosure relates generally to a jacketed bullet which utilizes a core-retaining feature within the jacket and a method of making the bullet and, more specifically, this disclosure relates to a three component bullet having an external locking band which ultimately forms a core-locking feature within the interior of the jacket such that the core remains locked within the jacket even after impact with a hard barrier material such as windshield glass or sheet steel, for example.
2.0 Related Art
In order for a bullet to achieve optimum terminal performance, its jacket and core must penetrate a target as a single unit and remain connected throughout the course of travel, regardless of the resistance offered by the target material.
Various attempts have been made over the years to keep a bullet's jacket and core coupled together on impact. One of the earliest and simplest attempts utilized a knurling method which created a “cannelure” in a jacketed bullet. A cannelure typically includes a narrow, 360° circumferential depression in the shank portion of the bullet jacket. While the cannelure was originally conceived for use as a crimping feature, various companies have attempted to use it as both a crimping groove and as a core retaining feature, or solely as a core retaining feature. The knurling process forces jacket material radially inwardly, subsequently creating a shallow internal protrusion which extends a short distance into the bullet core. This approach has generally proven ineffective in keeping the core and jacket together, primarily due to the limited radial depth involved and the minimal amount of longitudinal core-gripping area that a cannelure offers. Upon impact with a hard barrier material, the core tends to immediately extrude beyond the confines of the inner protrusion, subsequently sliding out of the jacket. Depending on jacket wall thickness, core hardness and impact energy, axial core movement can actually “iron out” the internal geometry of the cannelure as the core slides forward. Even multiple cannelures have proven ineffective due to the inadequate amount of square area they are collectively able to cover.
U.S. Pat. No. 4,336,756 (Schreiber) describes a “two-component bullet” intended for hunting which comprises a cold worked jacket utilizing a narrow, inwardly-extending annular ring of jacket material terminating in a “knife-like edge” which is formed from a thickened portion of the jacket wall and which engages and holds the base of the core within the jacket after the bullet is final formed. U.S. Pat. No. 4,856,160 (Habbe, et al.) also describes a “two-component bullet” utilizing a reverse taper on the rearward interior of the jacket to lock the core within the jacket.
Other attempts at retaining the core within the jacket have been used in the past which do not utilize an external locking band. Such attempts range from providing a “partition” separating a rear core from a front core, electroplating a copper skin around the core prior to final forming the bullet, and heat-bonding (or similar heat treatment) the core to the interior of the jacket wall after the bullet is final formed. Each of these methods has shortcomings. The shortcomings typically include one or more of the following: (a) Jacket-core eccentricity resulting in less than desirable accuracy due to bullet imbalance, (b) slow manufacture, (c) high cost, and/or (d) less reliable.
With respect to the use of an external “band” in the construction of a projectile, U.S. Pat. No. 4,108,073 (Davis) describes an armor piercing projectile having a “rotating band” which is positioned around the outer surface of the jacket near the rearward end of the projectile. The diameter of the rotating band is larger than the diameter of the jacket. The rotating band serves to impart rotation to the projectile as it passes through the gun bore and seals hot gasses within the bore. The band typically includes plastic, gilding metal, sintered iron or other well known rotating band material. The Davis patent as cited herein should be viewed as general information only as the rotating band concept serves a completely different purpose than the three-component invention disclosed herein.